I have been reading William James’s The Varieties of Religious Experience (1902). The book is interesting and thought-provoking, and covers a number of interesting subjects related to religion. In this passage (pp. 15-16), James discusses truth and feelings:

Let us play fair in this whole matter, and be quite candid with ourselves and with the facts. When we think certain states of mind superior to others, is it ever because of what we know concerning their organic antecedents? No! it is always for two entirely different reasons. It is either because we take an immediate delight in them; or else it is because we believe them to bring us good consequential fruits for life. When we speak disparagingly of ‘feverish fancies,’ surely the fever-process as such is not the ground of our disesteem for aught we know to the contrary, 103° or 104° Fahrenheit might be a much more favorable temperature for truths to germinate and sprout in, than the more ordinary blood-heat of 97 or 98 degrees. It is either the disagreeableness itself of the fancies, or their inability to bear the criticisms of the convalescent hour. When we praise the thoughts which health brings, health’s peculiar chemical metabolisms have nothing to do with determining our judgment. We know in fact almost nothing about these metabolisms. It is the character of inner happiness in the thoughts which stamps them as good, or else their consistency with our other opinions and their serviceability for our needs, which make them pass for true in our esteem.

Now the more intrinsic and the more remote of these criteria do not always hang together. Inner happiness and serviceability do not always agree. What immediately feels most ‘good’ is not always most ‘true,’ when ​measured by the verdict of the rest of experience. The difference between Philip drunk and Philip sober is the classic instance in corroboration. If merely ‘feeling good’ could decide, drunkenness would be the supremely valid human experience. But its revelations, however acutely satisfying at the moment, are inserted into an environment which refuses to bear them out for any length of time. The consequence of this discrepancy of the two criteria is the uncertainty which still prevails over so many of our spiritual judgments. There are moments of sentimental and mystical experience we shall hereafter hear much of them that carry an enormous sense of inner authority and illumination with them when they come. But they come seldom, and they do not come to every one; and the rest of life makes either no connection with them, or tends to contradict them more than it confirms them. Some persons follow more the voice of the moment in these cases, some prefer to be guided by the average results. Hence the sad discordancy of so many of the spiritual judgments of human beings; a discordancy which will be brought home to us acutely enough before these lectures end.

I have written on this subject as well, and even done my own small study of spiritual feelings in which I compare the descriptions of people from a diverse set of religions writing about their spiritual feelings. People from very different religions all describe similar spiritual experiences and feelings. Spiritual feelings thus do not appear to be reliable guides to objective truth, but they are good guides for finding truth about how we should act and be, and they help us draw closer to God.